1. Field of the Invention
The present invention generally relates to the illumination of large surfaces and, more particularly, to providing uniform illumination over large areas at a shallow depth which is particularly suited for automobiles.
2. Description of the Prior Art
In modern industrial design, there are a number of applications which call for illuminating large surface areas but the distance perpendicular to the surface area to be illuminated which is available for a light source is small. The problem then is to provide uniform illumination of a thin panel at an acceptable cost.
In one such application, automobile manufacturers have been adding large decorative reflectorized areas on the rear deck lids of some of their models. The reflectorized areas blend in well with the rear lighting on the quarter panels and have a pleasing appearance during the day. At night, however, these areas appear dark and unattractive. To light these large areas with incandescent lamps presents two problems. First, it is difficult to get even illumination over such a large area using point sources such as incandescent lamps. Secondly, the large accelerations experienced by lamps mounted on the rear deck lid when it is closed are sufficient to deform or even fracture the filament of the lamp. Light emitting diode (LEDs) may very well serve as an alternative light source so as to solve such incandescent lamp problems.
In another application, liquid crystal displays (LCDs) are commonly used for a variety of applications ranging from personal televisions to computer displays. One of the principal reasons for the popularity of LCDs is their small size and low power consumption. Current illuminators for LCDs use fluorescent lamps of high efficiency and light box cavities to provide uniform illumination. To make LCDs more acceptable, the LCDs are now generally provided with a source of back lighting. In order to retain the advantage of LCDs being used as a thin flat panel display, this back lighting source must also be thin. This type of design must be of a certain minimum thickness due to the lamp size and light box cavity size to achieve a uniform backlighting of the display.
Another type of illuminator which achieves uniform illumination over a large area and yet is thin is manufactured by Lumitex, Inc. The Lumitex device uses a high efficiency light source and collects and concentrates this light by focusing it into an optical fiber bundle. The fibers of the bundle are fanned out and woven into a flat panel. Light is made to leak from the woven panel by sharp bending of the fibers in the weave pattern. The disadvantages of this device are its cost of construction and the lack of directionality of the leaked light and efficiency when designed to achieve a high degree of uniformity.